Device for transporting a hollow body, installation provided with such devices, and method for conveying a hollow body attached to such a device

ABSTRACT

The preform conveying installation ( 2 ) comprises gripping members ( 6 ) and heads ( 7 ) for feeding them into the heating oven, and includes a detection system that selects preforms likely to cause incidents in said heating oven, and means for detaching each selected preform from its gripping head ( 7 ), which means apply pressure to the interior of the selected preform ( 2 ), on its base, and these consist of a nozzle ( 15 ) capable of directing a jet of pressurized fluid at said base. The gripping member ( 6 ) and the gripping head ( 7 ) comprise an orifice in the form of a bore ( 9 ) that enables the jet of pressurized fluid to be applied directly into the selected preform.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/FR2008/052074 filed Nov. 18, 2008, claiming priority based on FrenchPatent Application No. 0708110, filed Nov. 19, 2007, the contents of allof which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates in general to the field of manufacturingreceptacles made of thermoplastic material obtained after heating andblow molding of a hollow body commonly called a preform, and it relatesmore particularly to a conveying system comprising a series of transportdevices that are each furnished with at least one gripping memberdesigned to carry a preform for the purpose of making it travel in avertical position inside the installation.

Therefore, the invention applies to the in-line processing installationsfor the manufacture or processing of preforms made of thermoplasticmaterial such as PET, in which installations said preforms are movedindividually one after the other with the aid of transport devicescapable of holding them by their neck, so as to leave their body freefor the purpose of heating.

DESCRIPTION OF THE PRIOR ART

Routinely, a preform takes the general shape of a tubular cylindricalbody closed at one of its axial ends and extended at its other open endby a neck already having the final shape of the neck of the finalreceptacle and a collar extending substantially radially. In the rest ofthe description, “receptacle provided with a neck” is understood to beany hollow body having a neck, namely preforms, from which receptaclesare manufactured by blow molding or stretch-blow molding, that is to sayreceptacles having their final shape and having to undergo an additionalprocess (such as a step of labeling or filling).

In the particular case of the transport of preforms, in order to takethem to temperature by heating prior to the blow molding step, it isnecessary to provide a transfer device making it possible to take eachpreform by its neck (“gripping”) in order to move it into a heatingzone, usually a heat-conditioning tunnel oven, in which zone the body ofsaid preform is to be heated to the glass-transition temperature of thethermoplastic material, while remaining at a temperature below thecrystallization temperature.

To achieve this transfer, it is known practice to use transport devicesfurnished with gripping members which comprise a mandrel suitable forbeing engaged inside the neck of the preform (internal gripping) andwhich holds the latter simply by adhesion because of the presence of theforces of pressure and of friction.

In document FR 2 706 876, in the name of the Applicant, a device for theinternal gripping of preforms from a gripping head having a split-ringend is proposed.

According to the same principle of internal gripping, it is knownpractice, as proposed in document FR 2 794 109 in the name of theApplicant, to produce a system for conveying preforms formed of a set oftransport elements each comprising a gripping device furnished at itsend with an annular split ring formed of several sectors; when the ringis engaged internally in the neck of a preform, the sectors that areforced radially outward by elastic means are capable of pressing on theinner cylindrical surface of the neck.

Alternatively, it is also possible for the preform to be gripped on theouter face of its neck (external gripping) as described, for example, indocument FR 2 882 963 in the name of the Applicant.

When this preform enters the heat-conditioning oven, the preformundergoes a rotation on itself in order to allow an even heating overthe whole outer surface of the preform. When a preform is loaded intothe mold, both internally and externally, it is possible for the latternot to be axially aligned with the gripping head.

In this case, because the preform is out of line and because of itsrotary movement on itself, the body of the preform, and in particularits end, is capable of coming into contact with the heating lamps of theoven and of causing considerable damage by breaking them and also,sometimes, the preform can catch fire.

Therefore, in order to prevent these incidents, such as the damaging ofthe oven heating lamps, it is necessary to provide, before they enterthe oven, an operation of releasing of the preforms, that is to say anoperation which consists in ejecting all the preforms that are capableof causing incidents when they pass into the heating oven.

This releasing operation makes it possible, in a general manner, toprevent heating preforms which would have a design defect on enteringthe oven.

Document FR 2 872 805 in the name of the Applicant describes a systemfor releasing preforms.

Optical detection means are provided in order to determine whichpreforms are to be released and, under the effect of an appropriatecommand apparatus, such as a programmable controller, an ejection memberintervenes in order to take away the preforms in question, which thenfall into a recovery bin for example.

This system, although giving full satisfaction, is nevertheless complexto apply and, above all, it hampers the production rates of theinstallation; specifically, the response time of the ejection member,for the purpose of the releasing, is relatively long.

Moreover, because of the current production rates and therefore thespeed of progress of the preforms, it is not possible to eject a singlepreform because, due to the response time of the pneumatic commandmeans, several preforms are affected by the ejection member and, ingeneral, routinely three successive preforms are on average ejected.

Because of the cost of manufacturing the preforms, and in order toprevent the scrapping of preforms correctly placed on the gripping heador having no defect, it would be of particular value to produce a devicefor releasing preforms that allows the releasing of only the preformthat is incorrectly secured or is incorrectly formed; said device beingable to be applied at high rates of travel of the preforms. It wouldalso be of particular value to produce a releasing system that couldalso be applied to the releasing of the preforms but and also to anytype of hollow body.

Moreover, because of this releasing of several preforms placed onebeside the other, there are considerable free spaces in thepreform-conveying chain (three successive gripping heads). These largespaces between the preforms, in the oven, disrupt the heating of theother preforms when they pass in front of the lamps of said oven; theresult of this is defects in the evenness of heating of the preforms.

Moreover, a current change in the context of the manufacture of preformstends to reduce the dimensions of the collar, which becomes increasinglythin and increasingly wide, and hence more frequent gripping problems.

Therefore, it would also be particularly advantageous to produce areleasing system that is not dependent on the size of a collar providedon the neck of the hollow body.

SUMMARY OF THE INVENTION

The present invention therefore proposes to solve the various problemsassociated with the prior art with the aid of a system for releasinghollow bodies that makes it possible to release a single preform at highconveying rates, which system also does not depend on the dimensionalcharacteristics of the collar of said preform.

According to a first of its aspects, the present invention relates to aninstallation for conveying preforms to a processing unit such as aheating oven in which they are taken to an appropriate temperature inorder subsequently to be formed by stretch-blow molding, whichinstallation comprises:

-   -   gripping members which are carried by an endless conveyor chain        and which are each furnished with a gripping head in order to        carry said preforms and in order to transfer them into said        heating oven,    -   at least one detection system placed on the path of said        preforms upstream of said heating oven, which detection system,        such as a shape-recognition camera, selects the preforms that        are likely to cause incidents in said heating oven, such as, for        example, preforms the alignment of which does not correspond        with that of the main axis of their gripping head,    -   means for detaching each selected preform from its gripping        head,    -   an apparatus, such as a programmable controller, to command the        ejection of the selected preform according to the information        originating from said detection system,    -   means for retrieving the ejected preforms, and it comprises        means for applying a pressure to the inside of the selected        preform, on its bottom, and in particular a sufficient pressure        to overcome the forces of adhesion between said selected preform        and its gripping head, in order to detach them.

Still according to the invention, the means capable of applying apressure in the selected preform, on its bottom, consist:

-   -   of a nozzle capable of spraying a jet of pressurized fluid at        the bottom of said selected preform, and,    -   of an orifice in the shape of a bore arranged in the member and        in the gripping head of said selected preform, said jet of        pressurized fluid being administered when said bore passes in        front of said nozzle.

According to another stipulation of the invention, the bore, into whichthe pressurized fluid intended for the selected preform is injected,comprises an upstream aperture in the form of a funnel which has anarrowing of its cross section in the direction of the downstreamaperture.

Still according to the invention, the programmable controller used forcommanding the injection of the pressurized fluid comprises a programarranged in order to establish an appropriate phase for theadministration of said pressurized fluid to the selected preform, whichphase extends for a period substantially greater than the time taken bysaid selected preform to pass in front of the spraying nozzle so as toensure an injection time of said pressurized fluid into the bore that islong enough to ensure the ejection of said selected preform.

The invention also relates to the method for releasing preforms whilethey are conveyed to the heating oven, in order to eliminate eachpreform capable of creating an incident during its passage in saidheating oven, said method consisting:

-   -   in monitoring the preforms which pass by, before they enter said        heating oven, in order to detect, in said preforms, a flaw        capable of causing incidents in said heating oven,    -   in detaching each preform recognized as undesirable from its        gripping head, upstream of said heating oven, by applying an        appropriate force to the inside of the undesirable preform, on        its bottom, and in particular a sufficient force to overcome the        forces of pressure and of friction that are applied between said        undesirable preform and its gripping head,    -   in collecting the rejected preform in an appropriate container.

Still according to the invention, the releasing method consists inseparating the undesirable preform from its gripping head via aninjection, in an appropriate bore of said gripping head, of a jet ofpressurized fluid which penetrates the inner volume of said undesirablepreform.

According to another stipulation of the invention, the releasing methodconsists in anticipating the passage of the undesirable preform in orderto trigger the injection of the pressurized fluid into said preform andit also consists in maintaining this injection of said pressurized fluidat least until the gripping head has passed in front of the nozzle forspraying said fluid.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will now be described with the aid of an examplethat is only illustrative and in no way limiting of the scope of thepresent invention, and based on the following figure which represents aview in axial section of a device for transporting and gripping a hollowbody according to the invention, which device, in cooperation with ablowing nozzle, makes it possible to carry out an operation of releasingof the preforms.

DETAILED DESCRIPTION OF THE INVENTION

In a simplified manner, FIG. 1 represents a view in axial section of adevice 1 for transporting a hollow body, such as a preform 2 made ofthermoplastic material. The preform 2 has a body 3 extending in asubstantially longitudinal manner and a neck 4 separated from the body 3by a collar 5 extending in a substantially transverse direction.

The transport device 1 comprises a gripping member 6 with a grippinghead 7 capable of being secured to the preform 2, and preferably, ofbeing secured in a sealed manner to its neck 4.

Shown in FIG. 1 is an “internal” gripping of the preform 2 and of thetype described in the aforementioned document FR 2 794 109, that is tosay that the gripping head 7 is inserted inside the neck 4 and thereforepresses on the inner face of the neck 4.

However, it should be noted that the principle according to theinvention applies equally to an “external” gripping of the preform 2,that is to say when the gripping head 7 presses on the outer face of theneck 4, in general pressing on the thread 8 of the neck 4.

According to the invention, the gripping member 6 has at least one bore9 opening through the gripping head 7.

Therefore, according to a first application of the invention, thepreform 2 is capable of being separated from the gripping head 7 byinjection of a pressurized fluid (preferably compressed air at apressure of the order of at least several bar, from 2 to 5 bar) in thebore 9 then opening into the closed volume 10 which is formed by thebody 3 of the preform 2 secured to said head 7 and to do so whether thevolume 10 is perfectly sealed or not.

Alternatively, the inside of the preform 2 can be disinfected byinjection of a disinfecting fluid into the bore 9 opening into theclosed volume 10 which is formed by the hollow body 3 secured to saidhead 7.

In general, it is possible to inject any type of fluid through the bore9 having an appropriate interaction and/or a desired processing actionon the closed volume 10 which is formed by the hollow body 3 secured tothe head 7.

The bore 9 is therefore designed passing through the gripping member 6,in a substantially rectilinear manner inside said member 6. This bore 9is of generally cylindrical shape and is formed centrally in the member6, that is to say that considering the gripping member 6 defines a maingripping axis X-X, the axis X-X relative to which it is determinedwhether the preform 2 is correctly secured to the gripping head 7 and inline with the latter, then the bore 9 is substantially formed coaxiallywith the main gripping axis X-X.

More precisely, the gripping member 6 comprises a mandrel 11 having saidgripping head 7 and a gripping rod 12 to which said mandrel 11 isattached, preferably in a removable manner.

The bore 9 is therefore formed and hollowed both in the gripping rod 12and in the mandrel 11.

In order to limit the pressure losses during the injection of thepressurized fluid in the bore, said bore is designed to be substantiallyrectilinear inside the gripping member and it is advantageously of ageneral shape that is substantially cylindrical.

More precisely, the bore 9 has an upstream aperture 13 for the injectionof a fluid and a downstream aperture 14 in the gripping head 7. Theupstream aperture 13 has a narrowing of its cross section in thedirection of the downstream aperture 14.

At the upstream aperture 13, in order to allow a maximum quantity offluid to be channeled, directed and to enter the bore 9, it is thereforeprovided that the upstream aperture 13 has a larger cross section thanthe cross section of the majority of the bore 9, and in particularlarger than the cross section of the downstream aperture 14.

Even though what is shown in FIG. 1 is a transport device 1 with asingle central bore 9, it is also possible to provide several bores 9,for example placed concentrically with the main gripping axis X-X, or toprovide a bore 9 that is divided into several secondary bores allopening into the gripping head 7.

The present invention also relates, according to a second of itsaspects, and in a more general manner, to an installation for conveyinghollow bodies 2 comprising a plurality of transport devices 1 whichtravel in line one after the other on an endless chain, not shown, of atype that is known per se, as can be seen, for example, in theaforementioned document FR 2 872 805.

The conveying installation comprises means for injecting a jet of fluidsuch as a pressurized blowing fluid, for example at a pressure ofbetween 2 and 5 bar, in the knowledge that, on this type of machine, apressure is available of up to 40 bar, which means for injecting blowingfluid are directed toward a point of passage of at least one bore 9formed internally in a transport device 1 when it travels on the endlesschain.

Preferably, the injection means take the form of a blowing nozzle 15which is attached, secured to the chassis of the installation, notshown, which nozzle 15 is therefore directed toward a point of passageof the upstream aperture 13 of the bore 9 during the travel of thetransport devices 1 associated with the endless chain.

In order to prevent too great a loss of the fluid injected through thenozzle 15, said nozzle 15 is situated facing a point of passage of theupstream aperture 13 of the bore of the transport devices 1 and it isonly a very short distance from this upstream aperture 13, for exampleof the order of a millimeter, or even a few millimeters.

According to one application of the invention, the conveyinginstallation may also comprise detection means such as ashape-recognition camera (not shown in the figure but of a type knownper se), in order to reveal a defect of alignment of the body 3 of thepreform 2 with the main gripping axis X-X and the axis of the grippinghead 7, whereby it is determined whether the preform 2 transported bysaid gripping head 7 must be separated from the latter by the injectionof the pressurized blowing fluid.

The command of this injection may be carried out via a programmablecontroller which receives and processes the information originating fromthe detection means mentioned above.

This programmable controller comprises a program arranged to organizethe command of the injection of the pressurized fluid into the preformthat is recognized as having a defect that is likely to cause incidentsin the oven for heating these preforms.

The arrangement of the injection program comprises a phase that isappropriate for the administration of the pressurized fluid to theselected preform, which phase extends, for example, for a period that issubstantially greater than the time taken by said selected preform topass in front of the spraying nozzle so as to ensure an injection timeof said pressurized fluid into the bore that is sufficiently long toensure that said selected preform is ejected.

This injection phase is also arranged to allow an anticipation of thetriggering of the injection of the pressurized fluid into saidundesirable preform facing the passage of said undesirable preform infront of the nozzle 15 for spraying said fluid and for maintaining thisinjection of said pressurized fluid at least until the gripping head 7has completely passed in front of said nozzle 15 for spraying saidfluid.

The invention therefore makes it possible, in general, to produce amethod for conveying a preform 2 secured to a transport device 1, saidmethod comprising a step of injection of a fluid through at least onebore 9 designed to pass through said transport device 1 and opening intothe inner volume 10 of the body 3 of the preform 2 secured to saidtransport device 1.

According to another form of application of the invention, adisinfecting fluid is injected through the bore 9. Alternatively, apressurized fluid is injected, which makes it possible to separate thehollow body 2 from the gripping head 7.

Therefore, in summary, according to one application of the invention, itis detected, with the aid of the detection means, whether a preform 2 isout of alignment with the axis X-X or has a manufacturing defect. It isthen determined, with the aid of the programmable controller and ofappropriate programs and/or computing means, when the transport device 1with this preform, and more precisely its bore 9, will pass in front ofthe means 15 for injecting blowing fluid, in order then to command theinjection of this fluid in order to release the preform (or any hollowbody secured to a gripping head 7).

The response time of the fluid injection means is markedly faster thanthe response times of the piston-based pneumatic means according to theaforementioned prior art, which makes it possible to release only onepreform at a time.

Therefore, according to a first application of the invention, the hollowbody is capable of being separated from the gripping head by injectionof a pressurized blowing fluid in the bore then opening into the closedvolume that is formed by the hollow body secured to said head.

Alternatively, the inside of the hollow body can be disinfected byinjection of a disinfecting fluid into the bore opening into the closedvolume that is formed by the hollow body secured to said head.

More generally, the invention can find its place on an installation fortransporting necked receptacles, where it is sometimes necessary torelease the hollow bodies that have a defect, such as, for example, onleaving the preform blow molding unit.

1. An installation for conveying preforms to a processing unit such as aheating oven in which they are taken to an appropriate temperature inorder subsequently to be formed by stretch-blow molding, whichinstallation comprises: gripping members which are carried by an endlessconveyor chain and which are each furnished with a gripping head inorder to carry said preforms and in order to transfer them into saidheating oven, at least one detection system placed on the path of saidpreforms upstream of said heating oven, which detection system, such asa shape-recognition camera, selects the preforms that are likely tocause incidents in said heating oven, such as, for example, preforms thealignment of which does not correspond with that of the main axis oftheir gripping head, means for detaching each selected preform from itsgripping head, an apparatus, such as a programmable controller, tocommand the ejection of the selected preform according to theinformation originating from said detection system, means for retrievingthe ejected preforms, wherein it comprises means for applying a pressureto the inside of the selected preform, on its bottom, and in particulara sufficient pressure to overcome the forces of adhesion between saidselected preform and its gripping head, in order to detach them.
 2. Theinstallation as claimed in claim 1, wherein the means capable ofapplying a pressure in the selected preform, on its bottom, consist: ofa nozzle capable of spraying a jet of pressurized fluid at the bottom ofsaid selected preform, and, of an orifice in the shape of a borearranged in the member and in the gripping head of said selectedpreform, said jet of pressurized fluid being administered when said borepasses in front of said nozzle.
 3. The installation as claimed in claim2, wherein the bore, into which the pressurized fluid intended for theselected preform is injected, comprises an upstream aperture in the formof a funnel which has a narrowing of its cross section in the directionof the downstream aperture.
 4. The installation as claimed in claim 3,wherein it comprises means for injecting fluid at a pressure of from 2to 5 bar.
 5. The installation as claimed in claim 1, wherein theprogrammable controller used for commanding the injection of thepressurized fluid comprises a program arranged in order to establish anappropriate phase for the administration of said pressurized fluid tothe selected preform, which phase extends for a period substantiallygreater than the time taken by said selected preform to pass in front ofthe nozzle so as to ensure an injection time of said pressurized fluidinto the bore that is long enough to ensure the ejection of saidselected preform.
 6. A method for releasing a preform or preforms whilethey are conveyed to the heating oven, in order to eliminate eachpreform capable of creating an incident during its passage in saidheating oven, said method consisting: in monitoring the preforms whichpass by, before they enter said heating oven, in order to detect, insaid preforms, a flaw capable of causing incidents in said heating oven,in detaching each preform that is qualified as undesirable from itsgripping head, upstream of said heating oven, in collecting the rejectedpreform in an appropriate container, wherein it consists in applying anappropriate force to the inside of said undesirable preform, on itsbottom, and in particular a sufficient force to overcome the forces ofpressure and of friction that are applied between said undesirablepreform and its gripping head.
 7. The method for releasing a preform orpreforms as claimed in claim 6, wherein it consists in separating theundesirable preform from its gripping head via an injection, in anappropriate bore of said gripping head, of a jet of pressurized fluidwhich penetrates the inner volume of said undesirable preform.
 8. Themethod for releasing a preform or preforms as claimed in claim 6,wherein it consists in injecting the jet of fluid at a pressure of from2 to 5 bar.
 9. The method for releasing a preform or preforms as claimedin claim 6, wherein it consists in anticipating the passage of theundesirable preform in order to trigger the injection of the jet ofpressurized fluid into said preform and in maintaining this injection ofsaid jet of fluid at least until the gripping head has passed in frontof the nozzle for spraying said fluid.